It’s a simple question that you’ve probably never thought about: with all those birds flying around, how come you never see two birds crash mid-air? To answer this question, researchers put parakeets (aka budgerigars) into an air tunnel and had them fly towards each other. They found that birds have evolved a simple way to avoid mid-air collisions: each bird always veers right and changes altitude. The authors suggest that these same strategies could be applied to airplane guidance systems.